1. Field of the Invention
This invention relates to the punching of holes in thin sheet materials such as greensheets used in the manufacture of integrated circuit semiconductor package structures and, more particularly, to a method and apparatus for loading punch pins into a gang-punch apparatus which apparatus is used to form holes in a desired pattern in the greensheet thin sheet material.
2. Description of Related Art
In the manufacture of multilayer ceramic (MLC) substrates for integrated circuit semiconductor package structures, a plurality of green ceramic sheets (commonly termed greensheets) are formed by doctor blading a slurry containing a resin binder, a particulate ceramic material, solvents and a plasticizer, drying the doctor bladed sheet and cutting it into appropriate size sheets. Holes, commonly termed vias, are then punched in each of the greensheets in desired circuitry patterns to facilitate forming electrical interconnections through the sheet. Electrically conductive paste is deposited in the holes and in appropriate circuitry patterns on the surface of the greensheets, each of the patterned sheets stacked and laminated, and the assembly subsequently fired at a sintering temperature to form a MLC substrate.
The vias are formed in the ceramic material when the material is in its green state. Prior to being fired, the greensheets are easily deformed and the precision with which the via holes are formed is greatly dependent upon the use of apparatus which minimize distortion or disruption to the structural integrity of the greensheet other than forming the via hole. With the size of electrical components constantly being reduced through technical improvement the positioning of the via holes in the ceramic greensheets is becoming ever more restrictive. Further, with the increase in the quantity of the electronic circuits needed to make the electronic component package, the requirement for a larger number of vias per unit area of substrate is evident.
Large numbers of holes must be punched into a greensheet with a high degree of precision in order to properly position the holes. At the same time, this punching operation must occur very rapidly in order to produce the large numbers of greensheets that are necessary in the mass production of multilayer ceramic electronic components.
One method for punching greensheets is using a gang-punch apparatus. A gang-punch is a punch/die set where all the punches for a particular ceramic greensheet layer are mounted in a rigid plate. The gang-punch is used to punch the entire greensheet (layer) with a single stroke. A gang-punch has very high throughput and is cost effective for very high volume products. Typically a separate gang-punch is used to punch each layer of the MLC package.
A number of attempts have been made to provide a universal xe2x80x9cgang-punchxe2x80x9d apparatus which will economically and efficiently provide the means to make via openings in each of the different greensheets used to make the MLC product. One type apparatus utilizes an interposer mask which contains hole openings where holes are desired to be punched. In these type apparatus, a plurality of punch elements are arranged in a grid arranged over the greensheet which is covered by the interposer mask. The greensheet is positioned on a die having through openings corresponding to all the punch elements in the punch head. When the punch elements contact the interposer mask as the punch head is moved downwardly, the hole will be punched where the openings occur since the punch element would pass through the openings in the interposer mask and through the ceramic greensheet. In other areas covered by the interposer mask, i.e., where holes are not desired, the interposer mask will stop the punch element and be retracted into the punch head. A progressive gang-punch utilizes steel balls at locations of punches to be punched on the surface of the punch head which when a roller traverses the top of the punch head vias are punched only where steel balls are located.
A particularly desirable low-cost high-density gang-punch is shown in U.S. Pat. No. 6,223,636 assigned to the assignee of the present invention. The disclosure of this patent is hereby incorporated by reference. In this patent, a gang-punch apparatus is provided for punching selected hole patterns in greensheets. The gang-punch apparatus uses a program plate in a punch head which holds punch pins and which program plate is positioned intermediate the non-punching end of the punch pins and a clearance plate wherein punch pins not used for punching a layer of a particular greensheet are retracted during punching. At the other punch pin locations, the punch pins upon activation of the punch apparatus are extended through the lower portion of the punch apparatus through a greensheet and die to form vias in the greensheet. A preferred punch pin used in the gang-punch apparatus comprises an elongated shank or stem having a ball at its upper end and an opposed squarely cut-off lower end. The diameter of the ball is slightly larger than the diameter of the stem and is supported by the upper surface of a guide plate in the gang-punch apparatus to hold the punch pins. The punch pin may be made from any suitable material such as tungsten, tungsten alloy, steel, beryllium, titanium and is preferably a tungsten carbide material.
In general, the gang-punch tools of the prior art, and in particular, the punch tool disclosed in U.S. Pat. No. 6,223,636, utilizes a punch head composed of thin plates loaded with many thousands of precision tungsten carbide punch pins. The typical punch head holds in excess of 40,000 individual punches that must be loaded into the drilled holes in the punch head plates. Due to the high number of punches used and their fragile nature and small size and close fit into the holes in the punch head, it is important that a precision automated device be provided to load each punch pin into the punch head with little or no intervention from an operator.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an apparatus for loading punch pins into a punch apparatus such as a gang-punch apparatus used for punching vias in greensheets.
It is another object of the present invention to provide a method for loading punch pins into a punch apparatus such as a gang-punch apparatus for punching vias in greensheets.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, an apparatus for loading punch pins into a punch apparatus, i.e., a gang-punch, wherein the punch pins have an elongated shank of a first diameter and a larger spherical, cylindrical or other type head having a second larger diameter which punch pins are positioned vertically in a grid in a punch pin supply plate. The punch pins are transferred preferably one at a time to a punch pin receiver device which is positioned above the surface of a movable jaw with the lower end of the receiver device proximate the surface of the jaw. The jaw, together with a mating jaw, are then positioned over an opening to be filled in a punch pin holding plate of the gang-punch apparatus. The receiver device is moved over the jaw opening and the punch pin in the device is forced into the punch pin holding plate opening. The above steps are repeated until the desired number of punch pins are transferred to the gang-punch punch pin holding plate.
In another aspect of the invention, a preferred apparatus for loading punch pins into a gang-punch apparatus comprises:
a punch pin supply plate containing a plurality of openings in a grid in which a plurality of punch pins are positioned vertically, the punch pins having an elongated shank of a first diameter and a second larger diameter head which head rests on or is slightly above the upper surface of the supply plate;
a punch pin removal device for removing preferably a single punch pin from the supply plate into the punch pin removal device;
a left jaw and a right jaw each movable horizontally and each having an upper surface and a lower surface and a mating opening at each end thereof for receiving and holding a punch pin vertically;
a punch pin receiver device having an open upper end and an open lower end for receiving the removed punch pin from the punch pin removal device in a vertical orientation with the head upward, the lower end of the punch pin receiver device being positioned proximate the upper surface of the left jaw;
preferably a transfer conduit for transferring the punch pin from the removal device to the punch pin receiver device;
a punch pin blow down device for exerting a force on the punch pin in the punch pin receiver device;
a punch pin pusher device for exerting a force on the head of the punch pin; and
an X-Y table on which a gang-punch pin holding plate having a plurality of openings is secured thereto for positioning the gang-punch punch pin holding plate;
wherein a punch pin removed from the supply plate by the punch pin removal device is transferred to the punch pin receiver device, the left jaw and right jaw are mated and positioned over the gang-punch punch pin holding plate opening to be filled and the punch pin receiver moved over the opening and the punch pin blow down device forces the punch pin from the punch pin receiver into the opening in the jaws, the punch pin receiver and punch pin blow down devices are then moved away and the punch pin pusher device used to exert a force on the head of the punch pin forcing the punch pin partly into the gang-punch punch pin holding plate opening, the jaws are then moved away and the punch pin pusher device used to exert a force on the head of the punch pin forcing the punch pin into the gang-punch punch pin holding plate opening with the above steps being repeated until the desired number of punch pins are transferred from the punch pin supply plate to the gang-punch punch pin holding plate.
In an additional aspect of the invention, a method for loading punch pins into a gang-punch apparatus comprises the steps of:
supplying a gang-punch punch pin holding plate having a plurality of openings to be filled with punch pins, the punch pins having an elongated shank of a first diameter and a second larger diameter head which head is slightly above or supported by the upper surface of the holding plate;
positioning the gang-punch punch pin holding plate into a gang-punch punch pin loading apparatus described above;
removing a punch pin from the punch pin supply plate with the punch pin removal device;
transferring the punch pin into the punch pin receiver device;
moving the left and right jaws over the opening in the gang-punch punch pin holding plate to be filled;
moving the punch pin receiver device over the jaw opening;
forcing the punch pin from the receiver device into the jaw opening using the punch pin blow down device;
moving the punch pin receiver device and punch pin blow down device away from the opening in the gang-punch punch pin holding plate;
forcing the punch pin partly into the gang-punch punch pin holding plate using the punch pin pusher device to exert a force on the head of the punch pin;
moving the jaws away from the opening and forcing the punch pin into the gang-punch punch pin holding plate using the punch pin pusher device; and
repeating the above steps until the desired number of punch pins are transferred from the punch pin supply plate to the gang-punch punch pin holding plate.
The method and apparatus for loading punch pins into a gang punch as described above are preferably used with the low-cost high-density gang-punch described in U.S. Pat. No. 6,223,636, supra. The guide plate of the gang-punch of the patent (also termed herein gang-punch punch pin holding plate) would be filled with the punch pins and the guide plate then used in the gang-punch apparatus described in the patent. The punch pins have an elongated shank of a first diameter and a second diameter larger head and are axially slideably disposed in the vertical through holes of the guide plate and the head keeps the punch pin from falling through the openings in the guide plate.